fglgear.cpp

6 DOF Missle Simulation

    WOW = false;
    compressLength = 0.0;

    // Return to neutral position between 1.0 and 0.8 gear pos.
    SteerAngle *= max(GetGearUnitPos()-0.8, 0.0)/0.2;

    ResetReporting();
  }

  ReportTakeoffOrLanding();

  // Require both WOW and LastWOW to be true before checking crash conditions
  // to allow the WOW flag to be used in terminating a scripted run.
  if (WOW && lastWOW) CrashDetect();

  lastWOW = WOW;

  return vForce;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

void FGLGear::ComputeRetractionState(void)
{
  double gearPos = GetGearUnitPos();
  if (gearPos < 0.01) {
    GearUp   = true;
    GearDown = false;
  } else if (gearPos > 0.99) {
    GearDown = true;
    GearUp   = false;
  } else {
    GearUp   = false;
    GearDown = false;
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

void FGLGear::ComputeSlipAngle(void)
{
  // Transform the wheel velocities from the local axis system to the wheel axis system.
  RollingWhlVel = vWhlVelVec(eX)*CosWheel + vWhlVelVec(eY)*SinWheel;
  SideWhlVel    = vWhlVelVec(eY)*CosWheel - vWhlVelVec(eX)*SinWheel;

  // Calculate tire slip angle.
    WheelSlip = atan2(SideWhlVel, fabs(RollingWhlVel))*radtodeg;

  // Filter the wheel slip angle

  double SlipOutput, ca, cb, denom;

  if (WheelSlipLagFilterCoeff > 0) {
    denom = 2.00 + dT*WheelSlipLagFilterCoeff;
    ca = dT*WheelSlipLagFilterCoeff / denom;
    cb = (2.00 - dT*WheelSlipLagFilterCoeff) / denom;

    SlipOutput = ca * (WheelSlip + prevSlipIn) + cb * prevSlipOut;

    prevSlipIn = WheelSlip;
    WheelSlip = prevSlipOut = SlipOutput;
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
// Compute the steering angle in any case.
// This will also make sure that animations will look right.

void FGLGear::ComputeSteeringAngle(void)
{
  double casterLocalFrameAngleRad = 0.0;
  double casterAngle = 0.0;

  switch (eSteerType) {
  case stSteer:
    SteerAngle = degtorad * FCS->GetSteerPosDeg(GearNumber);
    break;
  case stFixed:
    SteerAngle = 0.0;
    break;
  case stCaster:
    // This is not correct for castering gear. Should make steer angle parallel
    // to the actual velocity vector of the wheel, given aircraft velocity vector
    // and omega.
    SteerAngle = 0.0;
    casterLocalFrameAngleRad = acos(vWhlVelVec(eX)/vWhlVelVec.Magnitude());
    casterAngle = casterLocalFrameAngleRad - Propagate->GetEuler(ePsi);
    break;
  default:
    cerr << "Improper steering type membership detected for this gear." << endl;
    break;
  }

  SinWheel      = sin(Propagate->GetEuler(ePsi) + SteerAngle);
  CosWheel      = cos(Propagate->GetEuler(ePsi) + SteerAngle);
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
// Reset reporting functionality after takeoff

void FGLGear::ResetReporting(void)
{
  if (Propagate->GetDistanceAGL() > 200.0) {
    FirstContact = false;
    StartedGroundRun = false;
    LandingReported = false;
    TakeoffReported = true;
    LandingDistanceTraveled = 0.0;
    MaximumStrutForce = MaximumStrutTravel = 0.0;
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

void FGLGear::InitializeReporting(void)
{
  // If this is the first time the wheel has made contact, remember some values
  // for later printout.

  if (!FirstContact) {
    FirstContact  = true;
    SinkRate      =  compressSpeed;
    GroundSpeed   =  Propagate->GetVel().Magnitude();
    TakeoffReported = false;
  }

  // If the takeoff run is starting, initialize.

  if ((Propagate->GetVel().Magnitude() > 0.1) &&
      (FCS->GetBrake(bgLeft) == 0) &&
      (FCS->GetBrake(bgRight) == 0) &&
      (FCS->GetThrottlePos(0) > 0.90) && !StartedGroundRun)
  {
    TakeoffDistanceTraveled = 0;
    TakeoffDistanceTraveled50ft = 0;
    StartedGroundRun = true;
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
// Takeoff and landing reporting functionality

void FGLGear::ReportTakeoffOrLanding(void)
{
  double deltaT = State->Getdt()*Exec->GetGroundReactions()->GetRate();

  if (FirstContact)
    LandingDistanceTraveled += Auxiliary->GetVground()*deltaT;

  if (StartedGroundRun) {
     TakeoffDistanceTraveled50ft += Auxiliary->GetVground()*deltaT;
    if (WOW) TakeoffDistanceTraveled += Auxiliary->GetVground()*deltaT;
  }

  if ( ReportEnable
       && Auxiliary->GetVground() <= 0.05
       && !LandingReported
       && Exec->GetGroundReactions()->GetWOW())
  {
    if (debug_lvl > 0) Report(erLand);
  }

  if ( ReportEnable
       && !TakeoffReported
       && (Propagate->GetDistanceAGL() - vLocalGear(eZ)) > 50.0
       && !Exec->GetGroundReactions()->GetWOW())
  {
    if (debug_lvl > 0) Report(erTakeoff);
  }

  if (lastWOW != WOW) PutMessage("GEAR_CONTACT: " + name, WOW);
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
// Crash detection logic (really out-of-bounds detection)

void FGLGear::CrashDetect(void)
{
  if ( (compressLength > 500.0 ||
      vForce.Magnitude() > 100000000.0 ||
      vMoment.Magnitude() > 5000000000.0 ||
      SinkRate > 1.4666*30 ) && !State->IntegrationSuspended())
  {
    PutMessage("Crash Detected: Simulation FREEZE.");
    State->SuspendIntegration();
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
// The following needs work regarding friction coefficients and braking and
// steering The BrakeFCoeff formula assumes that an anti-skid system is used.
// It also assumes that we won't be turning and braking at the same time.
// Will fix this later.
// [JSB] The braking force coefficients include normal rolling coefficient +
// a percentage of the static friction coefficient based on braking applied.

void FGLGear::ComputeBrakeForceCoefficient(void)
{
  switch (eBrakeGrp) {
  case bgLeft:
    BrakeFCoeff =  ( rollingFCoeff*(1.0 - FCS->GetBrake(bgLeft)) +
                     staticFCoeff*FCS->GetBrake(bgLeft) );
    break;
  case bgRight:
    BrakeFCoeff =  ( rollingFCoeff*(1.0 - FCS->GetBrake(bgRight)) +
                     staticFCoeff*FCS->GetBrake(bgRight) );
    break;
  case bgCenter:
    BrakeFCoeff =  ( rollingFCoeff*(1.0 - FCS->GetBrake(bgCenter)) +
                     staticFCoeff*FCS->GetBrake(bgCenter) );
    break;
  case bgNose:
    BrakeFCoeff =  ( rollingFCoeff*(1.0 - FCS->GetBrake(bgCenter)) +
                     staticFCoeff*FCS->GetBrake(bgCenter) );
    break;
  case bgTail:
    BrakeFCoeff =  ( rollingFCoeff*(1.0 - FCS->GetBrake(bgCenter)) +
                     staticFCoeff*FCS->GetBrake(bgCenter) );
    break;
  case bgNone:
    BrakeFCoeff =  rollingFCoeff;
    break;
  default:
    cerr << "Improper brake group membership detected for this gear." << endl;
    break;
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
// Compute the sideforce coefficients using similar assumptions to LaRCSim for now.
// Allow a maximum of 10 degrees tire slip angle before wheel slides.  At that point,
// transition from static to dynamic friction.  There are more complicated formulations
// of this that avoid the discrete jump (similar to Pacejka).  Will fix this later.

void FGLGear::ComputeSideForceCoefficient(void)
{
  if (ForceY_Table) {

    FCoeff = ForceY_Table->GetValue(WheelSlip);

  } else {

    if (fabs(WheelSlip) <= 10.0) {
      FCoeff = staticFCoeff*WheelSlip/10.0;
    } else if (fabs(WheelSlip) <= 40.0) {
      FCoeff = (dynamicFCoeff*(fabs(WheelSlip) - 10.0)/10.0
                + staticFCoeff*(40.0 - fabs(WheelSlip))/10.0)*(WheelSlip>=0?1.0:-1.0);
    } else {
      FCoeff = dynamicFCoeff*(WheelSlip>=0?1.0:-1.0);
    }
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
// Compute the vertical force on the wheel using square-law damping (per comment
// in paper AIAA-2000-4303 - see header prologue comments). We might consider
// allowing for both square and linear damping force calculation. Also need to
// possibly give a "rebound damping factor" that differs from the compression
// case.

void FGLGear::ComputeVerticalStrutForce(void)
{
  double springForce = 0;
  double dampForce = 0;

  springForce = -compressLength * kSpring;

  if (compressSpeed >= 0.0) {

    if (eDampType == dtLinear)   dampForce = -compressSpeed * bDamp;
    else         dampForce = -compressSpeed * compressSpeed * bDamp;

  } else {

    if (eDampTypeRebound == dtLinear)
      dampForce   = -compressSpeed * bDampRebound;
    else
      dampForce   =  compressSpeed * compressSpeed * bDampRebound;

  }
  vLocalForce(eZ) =  min(springForce + dampForce, (double)0.0);

  // Remember these values for reporting
  MaximumStrutForce = max(MaximumStrutForce, fabs(vLocalForce(eZ)));
  MaximumStrutTravel = max(MaximumStrutTravel, fabs(compressLength));
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

double FGLGear::GetGearUnitPos(void)
{
  // hack to provide backward compatibility to gear/gear-pos-norm property
  if( useFCSGearPos || FCS->GetGearPos() != 1.0 ) {
    useFCSGearPos = true;
    return FCS->GetGearPos();
  }
  return GearPos;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

void FGLGear::bind(void)
{
  char property_name[80];
  if (eContactType == ctBOGEY) {
    snprintf(property_name, 80, "gear/unit[%d]/slip-angle-deg", GearNumber);
    Exec->GetPropertyManager()->Tie( property_name, &WheelSlip );
    snprintf(property_name, 80, "gear/unit[%d]/WOW", GearNumber);
    Exec->GetPropertyManager()->Tie( property_name, &WOW );
    snprintf(property_name, 80, "gear/unit[%d]/wheel-speed-fps", GearNumber);
    Exec->GetPropertyManager()->Tie( property_name, &RollingWhlVel );
    snprintf(property_name, 80, "gear/unit[%d]/z-position", GearNumber);
    Exec->GetPropertyManager()->Tie( property_name, (FGLGear*)this,
                          &FGLGear::GetZPosition, &FGLGear::SetZPosition);
  }

  if( isRetractable ) {
    snprintf(property_name, 80, "gear/unit[%d]/pos-norm", GearNumber);
    Exec->GetPropertyManager()->Tie( property_name, &GearPos );
  }

}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

void FGLGear::Report(ReportType repType)
{
  switch(repType) {
  case erLand:
    cout << endl << "Touchdown report for " << name << endl;
    cout << "  Sink rate at contact:  " << SinkRate                << " fps,    "
                                << SinkRate*0.3048          << " mps"     << endl;
    cout << "  Contact ground speed:  " << GroundSpeed*.5925       << " knots,  "
                                << GroundSpeed*0.3048       << " mps"     << endl;
    cout << "  Maximum contact force: " << MaximumStrutForce       << " lbs,    "
                                << MaximumStrutForce*4.448  << " Newtons" << endl;
    cout << "  Maximum strut travel:  " << MaximumStrutTravel*12.0 << " inches, "
                                << MaximumStrutTravel*30.48 << " cm"      << endl;
    cout << "  Distance traveled:     " << LandingDistanceTraveled        << " ft,     "
                                << LandingDistanceTraveled*0.3048  << " meters"  << endl;
    LandingReported = true;
    break;
  case erTakeoff:
    cout << endl << "Takeoff report for " << name << endl;
    cout << "  Distance traveled:                " << TakeoffDistanceTraveled
         << " ft,     " << TakeoffDistanceTraveled*0.3048  << " meters"  << endl;
    cout << "  Distance traveled (over 50'):     " << TakeoffDistanceTraveled50ft
         << " ft,     " << TakeoffDistanceTraveled50ft*0.3048 << " meters" << endl;
    TakeoffReported = true;
    break;
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
//    The bitmasked value choices are as follows:
//    unset: In this case (the default) JSBSim would only print
//       out the normally expected messages, essentially echoing
//       the config files as they are read. If the environment
//       variable is not set, debug_lvl is set to 1 internally
//    0: This requests JSBSim not to output any messages
//       whatsoever.
//    1: This value explicity requests the normal JSBSim
//       startup messages
//    2: This value asks for a message to be printed out when
//       a class is instantiated
//    4: When this value is set, a message is displayed when a
//       FGModel object executes its Run() method
//    8: When this value is set, various runtime state variables
//       are printed out periodically
//    16: When set various parameters are sanity checked and
//       a message is printed out when they go out of bounds

void FGLGear::Debug(int from)
{
  if (debug_lvl <= 0) return;

  if (debug_lvl & 1) { // Standard console startup message output
    if (from == 0) { // Constructor - loading and initialization
      cout << "    " << sContactType << " " << name          << endl;
      cout << "      Location: "         << vXYZ          << endl;
      cout << "      Spring Constant:  " << kSpring       << endl;

      if (eDampType == dtLinear)
        cout << "      Damping Constant: " << bDamp << " (linear)" << endl;
      else
        cout << "      Damping Constant: " << bDamp << " (square law)" << endl;

      if (eDampTypeRebound == dtLinear)
        cout << "      Rebound Damping Constant: " << bDampRebound << " (linear)" << endl;
      else 
        cout << "      Rebound Damping Constant: " << bDampRebound << " (square law)" << endl;

      cout << "      Dynamic Friction: " << dynamicFCoeff << endl;
      cout << "      Static Friction:  " << staticFCoeff  << endl;
      if (eContactType == ctBOGEY) {
        cout << "      Rolling Friction: " << rollingFCoeff << endl;
        cout << "      Steering Type:    " << sSteerType    << endl;
        cout << "      Grouping:         " << sBrakeGroup   << endl;
        cout << "      Max Steer Angle:  " << maxSteerAngle << endl;
        cout << "      Retractable:      " << isRetractable  << endl;
        cout << "      Relaxation Velocities:" << endl;
        cout << "        Rolling:          " << RFRV << endl;
        cout << "        Side:             " << SFRV << endl;
      }
    }
  }
  if (debug_lvl & 2 ) { // Instantiation/Destruction notification
    if (from == 0) cout << "Instantiated: FGLGear" << endl;
    if (from == 1) cout << "Destroyed:    FGLGear" << endl;
  }
  if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
  }
  if (debug_lvl & 8 ) { // Runtime state variables
  }
  if (debug_lvl & 16) { // Sanity checking
  }
  if (debug_lvl & 64) {
    if (from == 0) { // Constructor
      cout << IdSrc << endl;
      cout << IdHdr << endl;
    }
  }
}

} // namespace JSBSim